CDMA receiver, path search method and program

a receiver and path technology, applied in the field of cdma receivers, can solve the problems of high power consumption, variation in the delay associated with the path to be rake combined, and also changes in the delay profile of the path, so as to achieve a small amount of calculation and power consumption

Inactive Publication Date: 2006-05-02
NEC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]It is an object of the present invention to provide a CDMA receiver and a path search method capable of performing, with a smaller amount of calculation and power consumption, the path search processing for discovering valid paths from a delay profile that has been obtained.

Problems solved by technology

However, because the relative position of a mobile station changes relative to a base station, the radio wave transmission environment around the mobile station varies and hence the delay profile also changes.
For this reason, the delay profile measured by the multipath searcher also varies, which results in variation in the delay associated with a path to be rake combined.
However, because there is generally a large amount of data and always a considerable amount of calculation required to obtain this correlation, a conventional path search method that performs the same correlation computation for all timings within the delay profile measurement range has inevitably taken considerable time to perform the processing required to detect paths from the delay profile, and its implementation has been associated with high power consumption.
A problem encountered with the conventional CDMA receiver described above is that because an enormous amount of computation is required in the path search processing for discovering valid paths from a delay profile that has been obtained, both the amount of calculation and the power consumption are large.

Method used

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  • CDMA receiver, path search method and program
  • CDMA receiver, path search method and program
  • CDMA receiver, path search method and program

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first embodiment

[0036]The functional block that calculates the delay profile generally has to cope with a large amount of computation and high power consumption. However, when there is little change in the paths and correlation peaks, it is assumed that a region in which there is no significant path will not have a path in the following sampling period either. Accordingly, the CDMA receiver of this first embodiment splits the delay profile measurement range into a plurality of regions and, before calculating the delay profile, integrates the plurality of regions in which a path (i.e., a correlation peak) was not present in the previous sampling period. This reduces the amount of computation required to calculate the delay profile, thereby decreasing the amount of processing and the power consumption.

[0037]FIG. 1 gives a block diagram showing the constitution of the CDMA receiver according to this first embodiment of the invention. As shown in FIG. 1, a CDMA receiver according to this first embodime...

second embodiment

[0072]FIG. 6 gives an example of correlation codes generated by combined correlation code generator 104 shown in FIG. 5. In the example given in FIG. 6, correlations would be calculated by taking the inner product of the data sequence and the code sequence C(j), C(j+1), . . . , C(n−1), C(n) for computing the correlation. Because this correlation code sequence is obtained by calculation, the value of data C(j−1) prior to the code sequence for computing the correlation, and the value of subsequent data C(n+1), can both be obtained by calculation. It is also possible to compute the correlation in any region using the same correlation code sequence. In this second embodiment, when region 11 and region 13 are to be combined, if a version of the correlation code that has been shifted by the delay difference between region 11 and region 13, i.e., a version of the correlation code shifted by delay difference i (see FIG. 6), is added to the original code sequence for computing the correlatio...

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Abstract

To perform path search processing by means of a smaller amount of calculation and less power consumption, region index calculator 29 decides, for each region resulting from subdividing the delay profile measurement range, whether or not it is a region in which there is a peak, and supplies the results of these decisions as index information. On the basis of this index information, region designation calculator 27 outputs information indicative of whether or not a given region is a region in which a path is present. On the basis of the information from region designation calculator 27, data classifier 24 classifies data, after analogue-to-digital conversion, into data of regions in which there is a path and data of regions in which there is no path. Data integrator 25 integrates the data of the plurality of regions in which no path is present, making it into data of a single imaginary region, and data combiner 26 combines the data of the regions integrated by data integrator 25, with the data of the regions in which there is a path. Delay profile measuring unit 33 forms a delay profile by calculating the correlation power of the combined data at each of a plurality of delays.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a CDMA receiver, and in particular to a method of searching for paths by calculating the delay profile at prescribed intervals, this delay profile showing the power distribution of the received signal as a function of delay.[0003]2. Description of Related Art[0004]In mobile communications, the spread in the propagation path lengths of the signal received in a multipath environment means that there are multiple waves having different propagation delays. A feature of direct sequence code division multiple access (DS-CDMA) is that it is capable of separating and extracting these multiple waves in the form of a so-called “delay profile”, by using a wide-bandwidth spreading code to spread the narrowband data. It is well known that in DS-CDMA communications a diversity effect can be obtained and receiving characteristics improved by rake combining this plurality of multipath signals with diffe...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): H04B1/69H04B1/707H04B1/7113
CPCH04B1/7113H04B1/7117
Inventor TERAO, KENJI
Owner NEC CORP
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